Apparatus for improving axial velocity profile of axial flow fans



Apnl 28, 1970 R. J. LIEVENS 3,508,842

APPARATUS FOR IMPROVING AXIAL VELOCITY PROFILE OF AXIAL FLOW FANS FiledOct. 8. 1968 INVEN'TOR. RONALD J. LIEVENS TORNEY United States PatentUS. Cl. 416-93 Claims ABSTRACT OF THE DISCLOSURE A fan having a novelhub attached to the fan wheel which directs induced air in a near axialdirection across the fan wheel improves the axial velocity profile.

BACKGROUND OF THE INVENTION This invention relates to fans and moreparticularly to a propeller fan having an improved axial velocityprofile.

Fans of the prior art move a gaseous fluid, for example air, in adirection parallel with the rotational axis of the fan blades. In manyaxial flow fans a high velocity is obtained at the periphery of therotating blades. The velocity decreases measuring radially inward,reaching a minimum at the point of connection between the blade and fanwheel. It is desirable to maintain a substantially constant axialvelocity as measured radially inward, thus improving the totalperformance of a given fan.

SUMMARY OF THE INVENTION This invention therefor provides a fan which ismounted for rotational motion and which includes a wheel having a frontportion and an outer portion, blades having a base portion attached tothe wheel, and means for rotatably driving this wheel. The improvementin the fan comprises a nozzle positioned at the outer, front portion ofthe wheel. The nozzle has an opening positioned to direct fluid flowingfrom the opening across the outer surface of the fan wheel and towardthe base portion of the blades. The nozzle also has means for supplyingit with the fluid as the fan rotates.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevational view ofa propeller fan embodying the nozzle of the instant invention.

FIGURE 2 is a front elevational view of the fan of FIGURE 1.

FIGURE 3 is a velocity profile typical of propeller fans of the priorart.

FIGURE 4 is a velocity profile typical of that obtained when the nozzleof the instant invention is utilized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGURES 1 and 2,fan wheel 2 is attached to drive member 4 via bolts 6. Drive member 4 isinte gral with motor shaft 5. The motor 7 can be any suitable drivingmeans for rotating the shaft 5 about its axis. For example, an electricmotor in direct drive relationship to shaft 5.

Blades 8 are attached to the fan wheel 2. The fan wheel 2 containsmachined, cast or molded channels 3 therein. Channels 3 run from thefront to the back of the fan wheel. The fan wheel and blades arepositioned concentrically within housing 9 by mounting means (notshown).

Removably attached to the front portion of fan wheel 3,508,842 PatentedApr. 28, 1970 2 is reentrant hub 10. The term front portion refers tothe part of the wheel upstream of the blades. In the embodiment shown inthe figures the reentrant hub is removably attached to the fan wheel bya threaded portion 11. The reentrant hub has a channel 14 thereincommunicating with the wheel channels 3. In this embodiment thereentrant hub has a circular peripheral cross secton when the section istaken across the hub axis. The reentrant hub overlaps a portion of thewheel 3 at 12 and is spaced from the wheel to form nozzles 13. In theembodiment of FIGURE 1, the nozzle of course is a toroidally shapedchannel. The nozzles 13 are communicating with the channel 14.

As the fan rotates, air or other fluid is drawn through the fan bladestoward the rear portion of the fan wheel and past the motor 7. As theair is drawn through the fan, a higher air pressure is built up at 15then exists at 16. This higher pressure at 15 causes air to enterchannels 3 from the rear, travel to the front of the fan wheel and enterchannel 14. From channel 14 the air or other fluid passes through theannularly shaped channel 13 across the outer surface of the fan wheel,thus wiping the outer surface of the fan wheel and the lower portion ofthe fan blade. This induced air flow greatly increases the axialvelocity of the air flow as measured radially outward from the axis ofrotation.

FIGURE 3 is a representation of the axial velocity of air or other fluidas it passes across the fan blades measured from a, the surface of thefan wheel, to b, the periphery of the blade. As it can be seen, theaxial velocity is low at a and high at b. FIGURE 4 shows the improvementin axial velocity radially outward from the fan wheel when the nozzle orreentrant hub of this invention is employed.

The reentrant hub of this invention eliminates undesirable axialvelocity profiles. As a result, fans using this concept have greatlyincreased performance. It is to be understood that the concept of thisinvention is applicable to all axial flow fans, including vane-axial andpropeller fans, although only a unitary embodiment of the invention hasbeen disclosed in the detail. Elimination of the undesirable velocityalso decreases sound level.

What is claimed is:

1. A fan mounted for rotational motion including a wheel having a frontportion and an outer portion, blades having a base portion attached tosaid wheel and a means for rotatably driving said wheel, wherein theimprovement comprises:

(a) a nozzle means positioned at the outer, front portion of said wheel,said nozzle having an opening positioned to direct fluid flowing fromsaid opening substantially tangentially across the outer surface of saidwheel, and toward the said base portion of said blades, the nozzle meanscomprising a hub having a rear portion which axially overlaps in aspaced relationship the said front portion of the said wheel, the saidrear portion of said hub and said wheel forming a nozzle around thefront portion of said wheel.

(b) supply means for supplying said nozzles with fluid when said fan isrotating, the said hub having a passage communicating with said supplymeans.

2. The fan of claim 1 wherein the said nozzle is attached to said wheel.

3. The fan of claim 1 wherein the said nozzle is attached to a portionof said drive shaft extending beyond the front portion of said wheel.

4. The fan of claim 1 wherein said hub has a substantially paraboliccross-section in plane in which the axis of said hub lies.

3 4 5. The fan of claim 1 wherein said supply means com- FOREIGN PATENTSprisgs (11131115518 in saig whgel fixtiil'ltdiflg from saiil flung969,292 5/1950 France por 1on o e rear 0 sa1 w ee 0 commumca e W1586,565 3/1947 Great B ritai n.

a high pressure fluid source.

References Cited 5 HENRY F. RA DUAZO, Primary Examiner UNITED STATESPATENTS US. 01. X.R. 1,851,513 3/1932 Holmstrom 170-156 415534162452,808,197 10/1957 Forgo 230-120 2,084,462 6/1937 Stalker 230 120 10

